The present invention relates to a roller assembly for feeding strip material. More particularly, the present invention relates to an improved feed roller assembly for use in apparatus wherein insulators, such as slot liners for dynamoelectric motors, are formed.
In the fractional horsepower motor art, stator core ground insulation often is in the form of slot liners that may be made from electrical insulating paper or from a polymerized material such as e.g., polyethylene terephthalate which may be purchased under the trade name "MYLAR" from E. I. du Pont de Nemours and Company. Slot liners may have a fold at one or both ends which form cuffs. When polymerized strip material is used it is often necessary to use a rubber coated feed roller to provide a consistent drive for the strip material because the friction characteristics of a smooth metallic roller usually are such that the driving action provided thereby is not sufficient to properly feed the strip material, without slippage, through slot liner forming apparatus. When electrical insulating paper is used, the feed rollers must avoid "ironing" or overpressing the fold in the slot liner and thereby rendering the cuff overly flat, yet the need for a consistent feed of material dictates that the roller maintain a proper driving relationship with the insulating paper.
In the past, feed rollers have been manufactured with a groove machined in the surface thereof, and rubber was molded therearound. The rubber was then ground so that its outer diameter was slightly greater than that of the grooved roller surface. When slot liner material was fed, the slot liner stock was then positioned relative to the feed roller so that the rubber was between the cuffs, and the rubber provided the drive for the insulating material. One of the disadvantages of this arrangement was that when wider slot liners were to be made and handled, the rubber was not wide enough to provide a consistent feed. On the other hand, if the rubber portion was made too wide, overpassing of the cuffs would result when a narrow slot liner was fed past the roller.
Heretofore, as the rubber part of a feed roller has worn down, its outer diameter decreased and then the distance between the rubber portion of the roller and an adjacent pinch roller increased, with the result that the rollers would have to be readjusted in order to properly drive the strip material. As the space between the rollers was decreased, however, more pressure would be applied to the multiple layers of strip material along the cuffs, and the cuffs would become "ironed" over or flattened. It should be noted that when the cuff is flattened objectionably it will not spring out after insertion into the slot of a magnetic core and thus it will not lock into position. This of course can result in a slot liner that is not in a desired proper position relative to a core slot during injection or placing of magnet wire into the core.
In view of the foregoing, it should now be understood that it would be desirable to provide an improved feed roller that would solve the above and other problems.
Accordingly, one of the objects of the present invention is to provide a roller assembly wherein a resilient feeding portion can be easily replaced.
Another object of the invention is to provide an improved roller assembly wherein the width of a resilient feeding portion of a feed roller may be readily changed.
Yet another object of the present invention is to provide a feed roller assembly for use in an insulator fabricating machine wherein the outer diameter of a resilient portion of the roller may be increased or decreased by a simple adjustment.